Conventionally, for a house or the like, a camera system including a camera installed at an entrance located inside or outside the house and a hub installed inside the house and connected to the camera has been widely used, for example.
PTL 1 discloses a system in which a master is connected to a public network such as the Internet via an adapter and a router and a cellular phone is connected to the public network. In such a system, when a call has arrived from a slave with a camera, the slave and the cellular phone can communicate with each other via the master, the adapter, the router, and the like.